The invention relates to a fuel supply system for an internal combustion engine having two separate fuel storage containers.
A fuel supply system of this type is known from DE 197 34 493 C1. This fuel supply installation is provided with a fuel tank for liquid fuel, from which a fuel feed line leads to an injection apparatus, with an evaporation and condensing device for low boiling-point fuel fractions, which is connected to the fuel tank, with an intermediate tank for the condensate, connected after the evaporation and condensing device, from which a condensate line leads to a control valve controlling the supply to the injection device, and with a residual fuel return line discharging the higher boiling-point residual fuel fractions accumulating in the evaporation and condensing device. The residual fuel return line opens into an additional tank, from which a residual fuel feed line leads to a changeover valve arranged in the fuel feed line. The control of the valve is such that, under full load of the internal combustion engine, the residual fuel from the residual fuel feed line is at least partly fed into the fuel feed line leading to the injection device.
WO 94/24432 discloses a method for monitoring the exhaust gas emissions of an internal combustion engine, which includes the extraction of a low boiling-point fuel fraction from normal gasoline or other liquid hydrocarbon fuels, the intention being for this low boiling-point fuel fraction to be fed to the combustion engine during a cold-start procedure in order to reduce the oxidizable contaminants in the exhaust gas of the internal combustion engine. This is to be done until the catalytic converter, which is used to reduce the contaminants in the exhaust gas of the engine, has reached its operating temperature. After that, the fuel supply to the engine is changed over to normal gasoline or other liquid hydrocarbon fuels.
Because of the compliance, required world-wide nowadays, with statutorily prescribed exhaust gas emission limiting values, a fuel supply installation having a fuel fractionation device for producing low boiling-point fuel fractions is needed on board a motor vehicle operated with internal combustion engines, in order to reduce the pollutant emissions arising during the operation of a motor vehicle in the cold-start and/or warm-up phase and to reduce the pollutant discharge overall. Previously known solutions feed low boiling-point fuel fractions on their own or mixed with the normal fuel to the internal combustion engine during a cold-start in order to reduce the pollutant discharge, the excess starting fuel frequently being consumed in the subsequent operating phases of the vehicle. This leads to increased starting fuel consumption.
It is therefore an object of the invention to provide a fuel supply installation for an internal combustion engine which, firstly, optimizes consumption of the starting fuel, and secondly has reduced pollutant emissions during the various operating phases of the motor vehicle.